The present invention relates generally to the application of pressure profiles to living tissues. More particularly the invention relates to a device for exerting an external pressure to a human body part and to a therapeutic garment.
External pressure profiles may be applied to living tissues, e.g. of a person's limb, in order to attain various effects with respect to these tissues. Perhaps the most well known example is the so-called G-suit worn by a pilot to restrict the blood circulation in his/her lower body parts under certain conditions, and thus reduce the risk that an insufficient amount of blood is fed to the pilot's head.
However, also in the medical field there are many examples of situations in which it is relevant/desirable to apply an external pressure to a part of the human body, in order to cure or mitigate a disease or condition. For instance, lymphoedema is a condition where the lymphatic system of a patient has been compromised, thereby resulting in a buildup of lymphatic fluids and proteins in one or more extremities. So far, various approaches have been attempted to control the swelling of the afflicted extremities. The compression-based treatment of lymphoedema is primarily dealt with in three ways, which may be combined to achieve an improved result, compression bandaging, pneumatic compression pumps and massage. The compression bandaging may be further divided into two general approaches: multi-layered lymphatic bandaging and elastic compression garments/bandages. Both these methods are used to statically compress the afflicted limbs, whereas pneumatic compression pumps and massage represent dynamic treatments.
Multi-layered lymphatic bandages are applied to a patient in order to reshape one or more of the patient's limbs. The bandages consist of absorbent layers, padding and short-stretch bandages. The absorbent layers must be custom made by a technician to fit the patient. Moreover, the underlying pressure is unknown after application, and the bandages are there to prevent the limb from further expanding and to breakup proteins with the help of patient movement. Nevertheless, these bandages are associated with numerous problems. During the treatment the bandages must be adjusted many times, for example because the bandages have a static shape and the shape of the limb varies over time. The bandages are also bulky and hot to wear due to the many layers applied to the limb, and therefore the bandages cannot be worn under clothing. Naturally, the therapy for the patient is limited in that the multi-layered lymphatic bandages cannot actively pressurize the body.
Elastic compression bandages are used to statically pressurize an afflicted limb. Here, a caregiver wraps the afflicted limb with a combination of elastic bandages and absorbent layers. The bandages are arranged so as to apply a graduated pressure to the limb. The pressure gradient along the limb is structured such that the highest pressure is at the distal end, and the lowest pressure is located at the proximal end of the limb. Hence, also in this case, the pressure application is static and a qualified person must apply the bandages to ensure that an appropriate pressure is accomplished, particularly since there is no convenient way to accurately measure the pressure applied to the limb. Normally, a constant bandage tension is applied while wrapping the limb, and the pressure graduation is typically a consequence of the limb being thinner at the distal part than at the proximal part. As the limb changes size due to the pressure, and as the bandages creep, the pressure application will decrease. This is true already within hours of applying the bandages.
A pneumatic compression pump device is used to dynamically pressurize limbs of patients. Here, dynamic pressurization is employed both to pump lymphatic fluids from the limb in wave-like, or graduated, pressure profiles and to breakup proteins that collect and harden in the afflicted limb. To generate the wave-like and graduated pressure profiles along the limb, a sleeve portion of the device must have multiple chambers. Each chamber is pressurized at the appropriate time as determined by the treatment prescription. However, the pneumatic compression pump devices are relatively inefficient, and therefore cannot operate from batteries for any significant length of time. In fact, it is normally required that the device be connected to mains power, and as a further consequence that the patient be stationary during the treatment. Since the pneumatic compression pump device is airtight, heat produced by the patient is accumulated in the device. Thus, the device can only be used for comparatively short durations before it becomes too uncomfortable for the patient. Although the device can dramatically reduce edema during treatment, after use, static compression bandages (or equivalent) must be applied to prevent the fluids from draining back into the afflicted limb. Additionally, the device is noisy, the air-pressure measurements used to infer pressure applied to the limb can be inaccurate, and unintentionally high pressure levels may harm the patient.
A qualified massage therapist/clinician may also apply various forms of massage to a patient. Such massage techniques are highly technical and require significant training to perform. Thus, the outcome of the treatment depends very much on the skill of the clinician.
U.S. Pat. No. 5,997,465 describes a device for exerting an external pressure on a human body, wherein the device surrounds a body part with a comfortable fit. The device includes memory material components, which alter their shape in response to an electric signal. Thereby, in a contracted state, these components may squeeze the body part, for example to prevent pooling of blood in the body part of a pilot when subjected to G-forces. Then, in a non-contracted state (i.e. when no electric signal is present) the memory material components resume their original shape, and the squeezing ceases. The electrical control proposed in this document overcomes some of the shortcomings associated with the above-described dynamic procedures, i.e. the pneumatic compression pump devices and massage forms. However, the solution is still inadequate for many medical applications. For instance, the skin of a patient is often compromised due to various medical conditions. In addition, the health of the patient's skin may lack elasticity, strength and resilience. Therefore, extreme care must be given to ensure that the pressure profile applied to the patient is medically safe. For instance, if highly localized pressures are applied for long periods of time, the tissues can tear and/or pressure ulcers may be formed. Moreover, if subjected to repeated rubbing, the skin can chafe, or even rip. Additionally, the medical treatments often require that the garments be worn for prolonged periods of time during which pressure and/or repeated pressure pulsation may be applied. Such activities further increase the risk of damage being caused to the patient's skin. Some medical applications may also require that the pressure profiles be variable over a very wide range, for example to promote fluid flow in superficial and interstitial tissues. Sometimes it is desired that the pressure profile emulate the naturally occurring function of a healthy body part.
The document EP 1 324 403 describes a motion augmentation solution, wherein an electroactive elastic actuator assists a patient to bend or unbend a joint. Although the document also briefly touches upon massage applications, there is no teaching or suggestion as how the actuators' pressure profiles may be modified, adjusted or by other means be smoothed out to meet various medical criteria.
The published U.S. patent application No. 2003/0212306 discloses electroactive polymer-based artificial muscle patches to be implanted adjacent to a patient's heart. The document also describes artificial sphincters to be implanted around the urethra, the anal canal, or the lower esophagus. Thus, the solutions exclusively aim at body internal pressure applications. Naturally therefore, the pressure transition issues are quite different from any implementations wherein pressures are applied to the outside of the body. For example, inside the body, due to the absence of nerves the patient cannot normally feel discomfort. Instead, it is here more important to prevent tissue death and calous formation near the edges of the patches.
U.S. Pat. No. 6,123,681 describes a polymer stocking for applying compressive forces to inhibit the development of thrombophlebitis. Interestingly, this document does not address the way in which pressure application is smoothed out over the limb. Instead, it appears most likely that the proposed polymer strips, which are relatively far spaced from one another risk to cause pressure ulcers and tissue damages. Moreover, improper materials are selected for the intended application because none of the polymer strips are capable of providing the high forces required in the thrombophlebitis treatment.